This invention relates to an adhesive film for semiconductor, a lead frame with adhesive film for semiconductor and a semiconductor device using the same.
Despite recent enlargement of semiconductor chips because of increases in functions and storage capacity, the packages housing them need small external shapes due to restrictions in designs of printed wiring boards and demands for downsized electronic apparatuses. To meet such tendency, there have been proposed some new mounting systems applicable both for semiconductor chips of increased density and for high-density mounting. Particularly, LOC structures proposed for memory elements, wherein leads are bonded on chips, can improve efficiency in interconnection of chips and wire bonding and shorten interconnecting lines, thereby speeding up signal transmission and downsizing packages.
In the new mounting system, bonding interfaces exist between different materials, such as semiconductor chips and lead frames, and their bonding reliability strongly influences the reliability of semiconductor packages. Not to mention to bonding workability and reliability tolerable to the processing temperatures during packaging, such bonding reliability as to tolerate to moisture absorption and wet heat and prevent package cracking during solder reflow for mounting on substrates is a matter of importance.
Paste adhesives or adhesives applied to heat resistant base materials have been used for bonding them. An example is a hot-melt type adhesive film using polyimide resins (Japanese Patent Application Non-examined Publication Nos. 5-105850 (1993), 5-112760 (1993) and 5-112761 (1993)). However, bonding with hot-melt type adhesives needs very high temperatures due to the high Tg of the adhesive resins, and tends to thermally damage semiconductor chips and adherents, particularly copper lead frames. Lowering the Tg gives adhesive films having low temperature adhesive property, but causes the problem of package cracking because the adhesive resins having lowered heat resistance reliability and increased elasticity cannot relieve the heat stress applied between chips and lead frames by the heat history during solder reflow for mounting on substrates.
This invention provides an adhesive film for semiconductor, which can be bonded at low temperatures in semiconductor devices.
This invention further provides a lead frame with adhesive film for semiconductor produced by punching the adhesive film for semiconductor to stick it to a prescribed position of a lead frame.
This invention further provides an extremely reliable semiconductor device containing a lead frame and a semiconductor element bonded together by the adhesive film for semiconductor.
The inventors of this invention have tried to develop adhesive films for semiconductor satisfying both low temperature adhesive property and reflow cracking resistance of semiconductor devices, with the result that they have found that the above-described problems can be solved by forming adhesive layers from an adhesive, which contains a heat resistant thermoplastic resin having specific properties, an epoxy resin and a trisphenol compounds as an epoxy resin-curing agent, and completed this invention.
Accordingly, this invention relates to an adhesive film for semiconductor (the adhesive film of the first invention), which has a three-layer structure consisting of a support film having each face coated with an adhesive layer, each adhesive layer containing (A) a heat resistant thermoplastic resin having a glass transition temperature of 130 to 300xc2x0 C., a water absorption of 3% by weight or less and a squeeze length of 2 mm or less, (B) an epoxy resin and (C) a trisphenol compound as an epoxy resin-curing agent.
This invention further relates to an adhesive film for semiconductor (the adhesive film of the second invention), which has a three-layer structure consisting of a support film having each face coated with an adhesive layer, each adhesive layer containing (A) a heat resistant thermoplastic resin having a glass transition temperature of 130 to 300xc2x0 C., (B) an epoxy resin and (C) a trisphenol compound as an epoxy resin-curing agent, wherein the adhesive film having the three-layer structure has a water absorption of 3% by weight or less and a squeeze length of 2 mm or less.
This invention further relates to a lead frame with adhesive film for semiconductor, comprising a lead frame and the adhesive film for semiconductor stuck to the lead frame.
This invention further relates to a semiconductor device, containing a lead frame and a semiconductor element which are bonded to each other with the adhesive film for semiconductor.